Spinning head

ABSTRACT

A spinning head in a melt spinning apparatus wherein a central conically shaped melt space between the upper cover or stem portion of the outer housing and the lower nozzle plate assembly contains a concavo-concave disk member arranged to provide a continuously narrowing flow path for the melt being received from a coaxial feed line and passing first outwardly and then inwardly, with reference to the spinning head axis, around the disk member to the nozzle plate assembly. This spinning head is especially adapted to handle synthetic linear fiber-forming polymer melts under high pressure, e.g., in spinning nylon filaments.

United States Patent 11 1 1111 3,762,850 Werner et al. 1 1 Oct. 2, 1973 [54] SPINNING HEAD 3,287,764 11/1966 Swickard et a1, 425/382 x 3,353,211 11/1967 Heijnis 1 1 425/464 [751 Inventors: 'f Elseflfeldf 3,397,428 8/1968 061111111 425 133 Wolfgang Grimm; Heinz Lmhart, both of Erlenbach of Germany Primary Examiner-.1. Spencer Overholser [73] Ass1gnee: AkzonaInc0rp0rated,Ashev1l1e, Ass/Stan, EXamine, Michaei 0. Sum,

Attorney-Johnston, Root et a1. [22] Filed: July 26, 1971 I 211 Appl. No.2 166,190 57 ABSTRACT A spinning head in a melt spinning apparatus wherein 1 Cl 8, 425/3822, 5/ a central conically shaped melt space between the [51] Int. Cl 1329f 3/04 upper cover or tem portion of the outer housing and [58] Field Of Search 425/198, 382, 463, the lower nozzle plate assembly contains a concavo- 425/464; 264/176 F concave disk member arranged to provide a continuously narrowing flow path for the melt being received [56] Ref l nC S Cited from a coaxial feed line and passing first outwardly and UNITED STATES PATENTS then inwardly, with reference to the spinning head axis, 2 970 340 2/1961 McDermmt 425/464 X around the disk member to the nozzle plate assembly. 2,879i543 3/1959 McDermott 425/198 x This p g head is especially fldapled handle y 2,891,278 6/1959 Cook 425/464 thetic linear fiber-forming polymer melts under high 3,225,383 12/1965 Cobb 425/198 X pressure, e.g., in spinning nylon filaments.

278,667 5/1883 Ols'zewski 1 1 425/464 3,229,330 1/1966 Ferrier et a1 425/198 X 10 Claims, 4 Drawing Figures II I 6 61 8 6111 I1 7 611 I2 7 l l R V/ l I ,1 I I, R V/ 44 w 1o y 3 PATENTED 2|975 3.752.850

SHEETlflF 2 INVENTORS" HELMUT WERNER WOLFGANG GRIMM HEINZ LINHART PATENTED 2 SHEET 2 [IF 2 FIGB INVENTORS:

NER N6 GRiMlvl Z LINHART HELMUT WER WOLFGA v HEIN sv goh w fiwtwwfiw,%wyy w.

SPINNING HEAD This invention generally relates to a spinning head for use in melt spinning apparatus, wherein the head includes a spinning nozzle plate as well as a distributor plate and/or a sieve pack stacked over the nozzle plate in a generally cylindrical assembly which is detachably connected by means of a flanged holder portion of an outer housing which includes an upper cover member having a coaxial feed line and wherein the melt space enclosed between the cover and the cylindrical nozzle plate assembly expands or flares conically outwardly from the inlet feed line to the distributor plate or to the superimposed sieve pack at the top of the nozzle plate assembly.

A spinning head of this type, which is suitable for the production of filaments, fibers, threads or the like composed of various high molecular weight polymeric spinning compositions, such as polyesters or polyamides, and in which a heated polymer melt is extruded under high pressure through the spinning openings of the nozzle plate, has been described for example in British Pat. No. 1,132,836. This patent also attempts to solve one of the most difficult problems in melt spinning, namely that of avoiding dead spaces in which the melt flow stagnates or eddies such that a thermal decomposition of the molten polymer material leads to a gradual stoppage of the flow path or individual channels therein. To solve this problem it is proposed in this British Patent to arrange a distributor element between the sieve pack and the housing cover in such a manner that the upper surface of the distributor forms with the lower or opposing surface of the housing cover a flow path narrowing toward the outside of the spinning head. This is designed to achieve above the distributor body a constant flow cross-section, which is then permitted to taper inwardly toward the center under the distributor element.

Although the spinning head described in this British Patent presumably brings about a uniform distribution of the melt over the entire sieve surface in the melt zone between the distributor element and the sieve pack, thereby contributing to a balancing of the spinning pressure over all the spinning nozzle bores or openings, it does not by any means provide a satisfactory solution to the problem of the gradual deposition and accumulation of decomposed polymer compositions. Such deposits still occur in this design of the spinning head, probably due in part as a result of the passage openings at the outer edge of the distributor element where the melt flow is suddenly severely constricted. In this known spinning head as well as in other spinning heads employed in this melt spinning art and fulfilling the general requirements of melt spinning apparatus, deposits rapidly form on the under-surface of the cover member, and after 2 to 4 days, these deposits cause the spinning head to become inoperable.

A primary object of the present invention is to considerably lengthen the running or operating time of the spinning head, even with very fine nozzle openings, largely by preventing deposits of thermally decomposed polymer melt compositions through the use of a specially designed flow guide member. Another object of the invention is to substantially avoid dead spaces in the flow of the polymer melt through the spinning head from its inlet or feed line to its nozzle plate assembly at the lower end thereof. Other objects and advantages of the invention are explained in greater detail hereinafter together with the following detailed specification.

In accordance with the invention, it has now been found that the specific problem of dead spaces and stoppage of spinning heads can be solved in a very practical and advantageous manner by means of a specially designed concave-concave flow guide member, preferably as a disk or very shallow biconical plate with rounded outer edges, which is centered in the conically expanded space extending from the feed line to the substantially cylindrical nozzle plate assembly arranged in an outer housing holder means which includes a cover or upper stem member through which the feed line extends coaxially to the spinning head. The centered flow guide or disk member is preferably supported only at a few widely spaced and selected points around its outer periphery such that the upper surface of the flow guide or disk member and the lower surface of the cover member define a melt flow path which narrows or converges outwardly away from the spinning head axis while the lower surface of the flow guide or disk member and the upper surface of the nozzle plate assembly define a melt flow path which narrows or converges inwardly toward the spinning head axis. The nozzle plate assembly preferably includes a distributor plate and/or a sieve pack mounted conventionally one over the other on top of the nozzle plate which contains the usual bores or spinning openings.

The concept of the present invention resides in part in providing melt flow surfaces internally of the spinning head between its feed line and its nozzle plate assembly which remain in contact with the flowing melt but do not present any marked profile changes or interruptions which may cause dead spaces in the melt flow. Most importantly, the flow cross-section must not expand in the direction from the feed line toward the nozzle plate assembly. lnstead, a gradual decrease or convergence of this flow cross-section preferably occurs over the entire path from feed line to nozzle plate assembly.

The term flow cross-section is employed herein in every instance for the annular, cylindrical or conical generated surface or planar segment perpendicular to the flow direction of the melt, i.e., where the melt flows through a disk or annular section along the spinning head and around the centered flow guide or diskshaped member.

Especially well suited for purposes of the invention'is a spinning head in which the flow guide member is a disk-shaped body which is symmetrical about its axis of rotation, i.e., about the spinning head axis, and which is preferably supported on three or more legs widely spaced at points around the periphery of the diskshaped body. In this manner, one can assure that the flow path is always bounded by relatively smooth surfaces without any abrupt changes of profile and that'no substantial constriction or retardation of melt flow occurs on the outer and preferably rounded edge of the flow guide or disk member. Instead, it is desirable that the melt, with reversal of its flow direction from inside-outside" to outside-inside around the flow guide member, retains its fluid velocity or slightly increases it.

In order to prevent the melt passing through the coaxially positioned feed line into the melt space from forming deposits at that central point on the upper surface of the flow guide element which represents a stagnation point and/or also to prevent dead spaces from arising in the immediate vicinity of the feed mouth or inlet to said space from the feed line, the upper surface of the disk-shaped flow guide element is preferably shaped toward the central axis of the spinning head in the form of a conically curved extension or displacement body portion, i.e., so as to curve gradually upwardly and inwardly to a point within the feed line, while the lower surface of the cover member running opposite to this conically curved extension also has a correspondingly gradually curved annular portion flaring outwardly from the feed line. The flow crosssection at this entry zone is then essentially formed by the oppositely disposed surfaces of the two conically curved or flared sections of the cover member and the flow guide or disk member, respectively.

The flow guide element or disk member, at its flow reversal point, i.e., at the transition from the upper surface to the lower surface corresponding to its outer-' most'periphery, expediently has a radius that lies preferably between about 2 and mm. in conventional sizes'of spinning apparatus. The spacing between this centered peripheral edge of the flow guide element and the interiorwall of the surrounding housing or holding means is preferably as uniform as possible and substantially free of interruptions in the melt flow path, so that the gradual reduction of the flow cross-section is also maintained or at least substantially maintained at this flow reversal point.

Finally, it is also expedient that the flow guide or disk member consist of a rustproof and acid-resistant steel, e.g., stainless steel or steel alloys, and that it also have polished surfaces.

The invention is explained in greater detail with the help of the accompanying drawing in which:

FIG. 1 is a vertical sectional view through the axis of a spinning head operated at normal spinning; pressure;

FIG. 2 is a similar vertical sectional view of another embodiment of a spinning head intended for spinning under higher pressures, for example up to about 250 atmospheres gauge pressure; and

FIG. 3 is a fragmentary sectional view at the rounded edge of centrally supported disk within the spinning head; and

H6. 4 is a fragmentary perspective view from inside the melt space toward the walls of the enclosure in FIG. 3

The spinning head illustrated in H0. 1 includes a nozzle cover 1 as a stem or upper part of the housing which also comprises a nozzle plate holder 2 in order to detachably connect the nozzle plate 3, the distributor plate 4 and the sieve pack 5 arranged into a common assembly or unit at the bottom or extrusion end of the spinning head The cover member 1 has a coaxial feed line or inlet conduit 8 which widens or flares outwardly at its bottom end, preferably over a circulararcuate curved surface section 1 into the lower conically widened surface 1' of the cover I. This lower surface 1' is thus directed conically outward to the sieve pack 5 or to the distributor plate 4, whichever is at the top of the nozzle plate assembly, and forms the overall melt space within the housing together with the upper surface 4' or 5 of the distributor plate 4.

In the large central space above the cylindrical nozzle plate assembly 3, 4 and 5 but below the cover or stem member 1, there is carefully positioned the flow guide element 6 which in FIG. 1 is supported by three narrow leg members 7 spaced equidistantly around the circumference of element 6 shaped in the form of a disk which bulges in the middle, i.e., so as to provide an upper surface 6' in combination with lower surface 1' of the cover 1 defining a gradually narrowing flow path or flow cross-section as the melt proceeds from the inlet 8 outwardly from the spinning head axis 9. The lower surface 6" of the disk insert 6 in combination with the upper surface 4' (or 5 of the nozzle plate assembly bounds a flow path narrowing inwardly toward the central axis 9. This flow guide insert 6 preferably has the form of a disk on the upper surface 6' of which there is seated or preferably integrally united a melt displacing element or curved conical extension 6" which extends coaxially up into the feed line 8. it is then also desirable that the feed line 8, as described above, includes a gradually curved transition 1' from line 8 into the surface 1'.

The small conical extension 6" on the upper surface 6' of the flow guide or disk member 6 is constructed, for example, so as to come to a point which lies on the central axis 9 of the spinning head and has a similar gradually curved transition into the surface 6'. Surfaces 1 and 6 narrow or converge on one another outwardly from the center of the spinning head in a manner which is preferably designed to cause at least a slight increase in the velocity or rate of flow of the relatively viscous and hot molten polymer. At the outer edge of the flow guide or disk member 6, the flow cross-section can temporarily widen slightly at the reversal point, i.e., in a plane extending perpendicular to the central axis 9 along the radial direction R as indicated. Then, surfaces 6" and 4 (or 5') likewise narrow or converge on one another from the periphery or reversal point toward the central axis 9, in this instance to essentially distribute the melt as uniformly as possible over the distributor plate 4 and/or sieve pack 5.

The guide member or disk 6 can be carefully centered by means of a centering ring 10 which can interlock or position supporting legs 7 and/or by means of a curved or at least sloped annular ring 11 forming a short segment of the wall surface at about the reversal point in the flow path down to the upper surface 4'(or 5') of the nozzle plate assembly. Suitable gaskets or sealing rings may also be used in a conventional manner in order to interconnect all of the elements of the spinning head, as by means of bolts 12 as illustrated in FIG. 1. Other preferred embodiments of suitable ring inserts and/or supporting legs are discussed more fully below in connection with FIGS. 3 and 4.

The spinning head constructed according to the invention as shown in FIG. 1 has proved most successful in actual practice, especially at relatively low and most conventional operating pressures. Operating periods of time of 265 hours and even more have been achieved with this spinning head without deposits or stoppages causing disturbances or cessation of the spinning process. Besides those advantages which the spinning head of the invention achieves in terms of an improved process, there should also be mentioned the purely structural advantages which reside in the fact that a simple guide element as a symmetrical body of rotation can be installed in the central melt space without channels, bays, baffles, passage apertures or the like that are difficult to tool or otherwise form. Moreover, this guide or disk element is quickly installed by means of a few simple manual operations into any spinning head of a melt spinning unit which otherwise fulfills the designated specifications or limitations of the invention. The extraordinary good results of the invention are then achieved, particularly a high quality spinning over greatly extended periods of time.

While in the spinning head operated at normal pressure as represented in FIG. 1, the individual elements are held together by means of screws or bolts 12, the high-pressure type of spinning head illustrated in FIG. 2 has a nozzle cover or inlet stem la and a nozzle plate holder 2a as housing elements which are screwed together as indicated at 13. The other individual parts or elements correspond generally to those of FIG. 1 and are therefore designated with the same numerals followed by the letter a.

With the high-pressure embodiment of FIG. 2, normal sieve arrangements in the sieve pack 5a can be used to achieve 92 atmospheres gauge pressure. With the use of especially thick sieve packs, 180 atmospheres gauge pressure can be achieved, and with the use of a conventional sand packing (not illustrated), 254 atmospheres gauge pressure can be attained as operating pressure. It is then possible to spin high viscous polyethylene terephthalate melts just as easily and free of trouble as with polyamide melts.

In order to very securely hold the flow guide or disk member 6a in the high-pressure spinning head of FIG. 2, it can be welded onto each narrow supporting leg 7a which is then centered or locked in place on the annular ring 10a. Surprisingly, the conical tip or pointed extension 6"'a appears to be much more significant in combination with the converging wall surfaces l'a and 6'a, especially in this high-pressure head, than is the careful design of the reversal point or the return zone adjacent the periphery of the disk 6a. Thus, this reversal point can also include annular sealing means 14 or the like which are not necessarily curved or streamlined but do function to make a perfectly sealed connection, for example between cover 1a and distributor plate 40.

On the other hand, for very sensitive or instable melt compositions which tend to decompose easily and/or to form precipitates or deposits or agglomerates during the spinning operation, the fiow reversal zone of the spinning head can also be carefully designed as indicated in FIGS. 3 and 4 to achieve a relatively smooth and substantially non-interrupted flow of the gradually thinned melt stream. The central flow guide or disk 6b, shown in partial section in FIG. 3 but omitted from the perspective of FIG. 4, has an upper surface 6'b spaced carefully to gradually converge with the surface lb of the cover member lb.

This disk 6b is supported in this instance upon three or more, preferably not more than about seven, supports in the form of wedge-shaped legs 71), each of which preferably tapers upwardly to the leading sharp edge 7'b from a slightly curved triangular tailing edge or face 7"b. The supporting curved edge 7"b of this leg can also be a relatively sharp edge or may also be a flattened triangular elongated segment extending out to the sharp edge 7'b while its base forms the upper side of a trapezoidal tailing face (not illustrated). These and similar modifications are desirable so that there is no sudden transition or obstruction in the melt path as it returns from the reversal point over these supporting legs. Such legs 7b can be welded or otherwise firmly attached to the centering ring 10b which also preferably presents a gradually curved wall surface 10''). These embodiments, which ensure a gradually narrowing flow path for the melt, are especially useful in relatively small spinning heads and/or in operating at high pressures where thin legs or a very small number of legs do not provide adequate support for the central flow guide or disk member.

In all of the illustrated spinning heads the nozzle plate 3 or 3' and distributor plate 4 or 4a contain a large number or conventional bores 15 and 16, respectively, associated with spinning orifices or openings arranged in a conventional pattern on the outer or bottom face of the nozzle plate 3 or 3a.

The spinning head of the invention has proved to be especially applicable in the spinning of a nylon 6,6 (polyhexamethylene adipamide) to which there are added stabilizing agents, which had previously resulted in especially severe deposits and early stoppage. A continuous spinning time of up to 265 hours was achieved with the spinning head constructed according to the invention when using this same nylon 6, melt composition.

The particular design of the spinning head as prescribed hereinabove and in the accompanying claims is obviously economical both in its manufacture, e.g., as a single-piece construction of the guide or disk insert, and also in its assembly using otherwise relatively conventional parts or assemblies. At the same time, substantially improved spinning results are achieved not only in fewer interruptions and longer operating periods but also in terms of a consistently uniform spun product. Although such spinning heads are best designed for spinning conventional linear polyamide and polyester (polyethylene terephthalate) melts, other high molecular weight, linear, fiber-forming polymers may also be spun with the apparatus of the invention.

The invention is hereby claimed as follows:

1. In a melt spinning apparatus having a spinning head in which a cylindrical nozzle plate assembly is detachably connected to a coaxial feed line by an outer housing holder means including a cover member defining a space which expands conically from said feed line to said nozzle plate assembly, the improvement comprising a concavo-concave fiow guide member centered in said space between said cover member and said nozzle plate assembly such that the upper surface of said flow guide member and the lower surface of the cover member define a melt flow path which narrows outwardly away from the spinning head axis and said feed line while the lower surface of said flow guide member and the upper surface of said nozzle plate assembly define a melt flow path which narrows inwardly toward the spinning head axis.

2. A melt spinning apparatus as claimed in claim 1 wherein said nozzle plate assembly includes a distn'butor plate and a sieve pack mounted one over the other on top of the nozzle plate.

3. A melt spinning apparatus as claimed in claim 1 wherein said flow guide member is a disk-shaped body symmetrical about the spinning head axis and supported centrally of said space between said cover member and said nozzle plate assembly by a plurality of widely spaced leg members at points around the periphery of said disk-shaped body.

4. A melt spinning apparatus as claimed in claim 3 wherein said disk-shaped body has a rounded outer peripheral edge with the radius of curvature of said edge being approximately 2 to 5 mm.

5. A melt spinning apparatus as claimed in claim 1 wherein said flow guide member is composed of a rustproof and acid resistant steel with polished upper and lower concave surfaces.

6. A melt spinning apparatus as claimed in claim 1 wherein the upper surface of said flow guide member has a central gradually curved portion extending inwardly toward the axis of the spinning head and upwardly into said feed line while the oppositely disposed lower surface of said cover member has acorrespondingly gradually curved annular portion flaring outwardly from said feed line.

7. A melt spinning apparatus as claimed in claim 6 wherein said central gradually curved extension together with the concave upper and lower portions of said flow guide member provide an integral outer diskshaped surface composed of a polished, rustproof and acid-resistant steel.

8. A melt spinning apparatus as claimed in claim 1 wherein said flow guide member is a disk-shaped body with a conically curved extension on its upper concave surface and with rounded outer peripheral edges, said cover member being correspondingly curved in an annular conical section extending into the feed line.

9. A melt spinning apparatus as claimed in claim 8 wherein an annular flow guide ring is positioned below and adjacent the outer periphery of said disk-shaped body to provide a smooth and substantially uninterrupted annular flow path around the outer edge of said disk-shaped body.

10. A melt spinning apparatus as claimed in claim 9 wherein said disk-shaped body is centrally supported in the melt space by leg members bridging the annular flow path around the outer edge of said disk-shaped body.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Paten 2,762.8s0 Q:-LtobeL 2, 1913 Invent fl Helmut Werner et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

First a e, left-hand column, ninth line, insert [20? Foreign Application Priority Data 27, o o I 0 o P -''I First page, right-h n column, Abstract, line 2, insert before "shaped".

Column l, line 17, "1" should read 1' Column 6, line 10, "or" should read of Column 6, line 21, "6," should read 6,6

Signed and sealed this 29th day of October 1971;.

(SEAL) Attest:

McCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents ORM PO-1D5O (10-69) USCOMM-DC 6376-P69 U.S. GOVERNMENT PRINTING OFFICE I969 0-365-384, 

1. In a melt spinning apparatus having a spinning head in which a cylindrical nozzle plate assembly is detachably connected to a coaxial feed line by an outer housing holder means including a cover member defining a space which expands conically from said feed line to said nozzle plate assembly, the improvement comprising a concavo-concave flow guide member centered in said space between said cover member and said nozzle plate assembly such that the upper surface of said flow guide member and the lower surface of the cover member define a melt flow path which narrows outwardly away from the spinning head axis and said feed line while the lower surface of said flow guide member and the upper surface of said nozzle plate assembly define a melt flow path which narrows inwardly toward the spinning head axis.
 2. A melt spinning apparatus as claimed in claim 1 wherein said nozzle plate assembly includes a distributor plate and a sieve pack mounted one over the other on top of the nozzle plate.
 3. A melt spinning apparatus as claimed in claim 1 wherein said flow guide member is a disk-shaped body symmetrical about the spinning head axis and supported centrally of said space between said cover member and said nozzle plate assembly by a plurality of widely spaced leg members at points around the periphery of said disk-shaped body.
 4. A melt spinning apparatus as claimed in claim 3 wherein said disk-shaped body has a rounded outer peripheral edge with the radius of curvature of said edge being approximately 2 to 5 mm.
 5. A melt spinning apparatus as claimed in claim 1 wherein said flow guide member is composed of a rustproof and acid resistant steel with polished upper and lower concave surfaces.
 6. A melt spinning apparatus as claimed in claim 1 wherein the upper surface of said flow guide member has a central gradually curved portion extending inwardly toward the axis of the spinning head and upwardly into said feed line while the oppositely disposed lower surface of said cover member has a correspondingly gradually curved annular portion flaring outwardly from said feed line.
 7. A melt spinning apparatus as claimed in claim 6 wherein said central gradually curved extension together with the concave upper and lower portions of said flow guide member provide an integral outer disk-shaped surface composed of a polished, rustproof and acid-resistant steel.
 8. A melt spinning apparatus as claimed in claim 1 wherein said flow guide member is a disk-shaped body with a conically curved extension on its upper concave surface and with rounded outer peripheral edges, said cover member being correspondingly curved in an annular conical section extending into the feed line.
 9. A melt spinning apparatus as claimed in claim 8 wherein an annular flow guide ring is positioned below and adjacent the outer periphery of said disk-shaped body to provide a smooth and substantially uninterrupted annular flow path around the outer edge of said disk-shaped body.
 10. A melt spinning apparatus as claimed in claim 9 wherein said disk-shaped body is centrally supported in the melt space by leg members bridging the annular flow path around the outer edge of said disk-shaped body. 